194 THE BUILDING OF EASTERN AUSTRALIA 



stratum of rock lying between two impervious strata. It 

 is also established that formations pervious enough to 

 become artesian beds have never been strongly compressed 

 by earth movements or regional metamorphism. They 

 have been areas of tensional strain and fracture since the 

 artesian beds were laid down, for which reason they in 

 most cases signify that elevation relative to adjoining seg- 

 ments of the earth's crust, has been the dominant earth 

 movement. 



In Eastern Australia Artesian Water may be found in 

 the Triassic (as in New South Wales, see Pittman) [39], 

 and in the Cretaceous (see Jack and Ethoridge, Geology 

 of Queensland.) Tertiary formations may also contain 

 Artesian (subartesian) Water, as in the Riverina and parts 

 of Victoria. 



Two theories as to the origin of the Australian Artesian 

 Water beds have been advanced, neither of which has been 

 properly established. 



The one school of geologists, supported by Pittman 

 and David, believe in the meteoric origin. They believe 

 that the pervious beds are continuous over vast areas, 

 and have outcrops on the surface near the edge of the 

 artesian basin, at which outcrops water is taken in from 

 streams that cross them. Water then rises in the bores 

 by hydrostatic pressure. The comparative freshness of 

 the water is supposed to be due to its having outlets to the 

 sea in the Gulf of Carpentaria and Great Australian Bight. 

 This view receives some support from the rapid dwindling 

 of Queensland rivers which cross the Blythesdale Bray- 

 stone (Cret.) in Queensland ; from a similar disappearance 

 of the streams that enter the Pilliga Scrub from the 

 Warrumbungle Mountains, in N.S.W. ; from the drying- 

 up of the Castlereagh River, west of Mundooran, and 

 many other such occurrences. 



The other school follow, Professor Gregory [40], in 

 believing that the water is nascent plutonic water, given 

 ofE by cooling igneous magmas at great depths. According 

 to this view, the porous artesian beds act as sponges, 

 absorbing the water which rises as subterranean 

 springs along joint cracks and other flows in the formation. 

 Gas and steam pressure would be the expelling forces. 



